Investigating accidents

The aftermath of the Ladbroke Grove accident on the approaches to London’s Paddington Station in 1999 had many far-reaching consequences. The training of drivers in the post-privatised railway and the implications for sighting of signals when a line is subsequently electrified with OLE structures led to many changes to the then current practice.

A joint investigation with the teams that led the investigations into this accident and the earlier one at Southall, culminated in the adoption of the Train Protection and Warning System (TPWS) that has largely overcome the risk of SPAD (Signal Passed at Danger) incidents, itself the prime cause of Ladbroke Grove and the multiple fatalities that resulted.

Not so well known was the recommendation to establish an independent accident investigation body to delve into the operating, technical and engineering elements of any future rail accident. The recommendation was taken forward by government and resulted in the formation of the Rail Accident Investigation Branch (RAIB). This would be an equivalent of the AAIB (Air Accident Investigation Branch) that investigates civil aviation accidents.

To learn more about the RAIB, the IET Rail Network invited Carolyn Griffiths, the chief inspector of rail accidents, to deliver its annual lecture and talk about the scope and type of work undertaken.

How the RAIB operates

The RAIB has been operational since 2005. Although part of the DoT for administration purposes, it is independent of all parts of the rail industry. The chief inspector reports directly to the Secretary of State. Its work covers all significant elements of rail: main line, metros, light rail, tramways, heritage lines, narrow gauge lines and also the Channel Tunnel in conjunction with the French. It has two bases, in Farnborough and in Derby, the latter having modest workshop facilities where equipment investigations can be carried out.

The team consists of 26 rail professionals – the chief inspector and her deputy, five principal inspectors and 19 inspectors. Carolyn Griffiths began her rail career in 1979 in the field of traction and rolling stock, at some point managing the train depot in Brighton, establishing the maintenance regime for the Singapore Metro and being the engineering director of South Yorkshire Supertram during its construction and early operations.

The inspectors have their individual specialisms in rail engineering and operations but everyone will have gone through the RAIB’s comprehensive training scheme such that all inspectors have a capability in every aspect of rail engineering, operations and human factors plus investigation skills. The RAIB is a 24/7 operation and inspectors can deploy within 30 minutes of an accident notification. They have the right to access accident sites and will usually have primacy.

To date, some 436 accidents/ incidents have been investigated with 241 reports being published. It is a requirement on the rail industry that specific accidents and near misses are reported to the RAIB and it is the latter’s decision as to whether the incident requires a formal investigation. Investigations are selected for those occurrences which are likely to result in recommendations that deliver significant improvements to safety and are not led simply by the industry’s perception of risk although risk assessment in all its scope will enter the process.

Around 70% of accidents arise on main line railways with metros and light rail forming the bulk of the remainder.

Predominant causes

Since the RAIB was set up, two areas of concern have become dominant. These are level crossings and the safety of track workers. Other significant ones are train derailments (mainly freight trains) and the poor condition of some earthworks and structures.

Level crossings, by their very nature, involve members of the public and their sometimes-unsafe behaviour. This is not restricted to car and lorry drivers, since pedestrian and farm track crossings are a big risk area.

Familiarity breeds contempt is a familiar phrase but there are other factors that lead people to act in a non-compliant way. Weather is one of these where sun glare can prevent people from seeing crossing lights.

Excessive wait times cause frustration or the belief that something is not working; an accident at a user worked crossing with telephone assistance on the Sudbury branch at Sewage Works Lane had a wait time of between six and twelve minutes. No surprise that lorry drivers with a schedule to keep would go across without permission and the inevitable collision happened.

Network Rail now has a dedicated team of experts – level crossing managers – to look at level crossing incidents and to better understand the behaviour of users. Some astonishing research has been done by RSSB on crossing user behaviour and the report is just published.

All too often track workers are being seriously injured or even killed.

A recent incident at Saxilby resulted in the fatality of the PICOW and the ensuing investigation revealed many shortcomings. Competence is at the crux of this, where unsafe behaviour, inadequate safety leadership and the unwillingness to challenge authority when unsafe situations arise are all too frequently encountered.

The solution is to enhance the competence of safety critical workers, improve the provision of information to them, minimise work on tracks that are open to traffic and to automate inspection of track conditions. Network Rail is introducing an initiative in the New Year aimed at tackling the competency and authority of persons in charge of site safety.

A worrying occurrence is the collapse of civil structures and earthworks. Whilst there have been incidents linked to recent extreme weather, by no means can all be blamed on this cause. These need to be carefully watched as several have happened in recent times. A history of incomplete reporting of long-term faults has to be put right and an enhanced examination regime put in place. Improved processes have since been adopted by the industry.

Electrical failures are thankfully rare, but a flashover at St Pancras International due to a defective lightning arrestor coupled with a wrongly installed line breaker caused the overhead line to break, with
the single catenary wire dropping down to platform level. Mercifully no-one came into contact with
this. Incorrectly installed protection equipment was the cause.

On the Tyne and Wear Metro, a substation inter tripping equipment did not activate immediately in reaction to a fault with a train’s line breaker equipment. This led to a fire with substantial damage to the car and associated electrical equipment.

Accidents with multiple causes

Two case studies of freight train derailments were described, by coincidence they happened on the same day, 15 October 2013. The first, at Camden Road, involved a container train from Birmingham to Felixstowe where the fifth wagon derailed, the containers fell off and collapsed the OLE. The two containers loaded on the wagon had different weights – 28.8 tonnes and 3.9 tonnes – thus causing both lateral and longitudinal asymmetric loading. The track, meanwhile, had a geometry fault with considerable track twist.

This combination of wagon and track imperfection caused the derailment. The subsequent investigation resulted in the accumulation of data for a number of similar derailments such that the sensitivity of loading conditions is much better understood.

The second accident, near Gloucester, occurred with the rear wheelset of the rear wagon in a container train becoming derailed at 69mph. Such is the power of modern diesel freight locomotives that the train ran on for a further four miles causing much damage with the wagon instability eventually causing the container to be thrown off. The cause was found to be a water and drainage deficiency with blocked drains and wet mud penetrating the track bed, thus causing considerable ‘cyclic top’ and bounce.

The location was known as problematic and should have had a 30mph speed restriction applied. However the speed and load of the wagon was also a factor. Computer modelling commissioned by the RAIB allowed a simulation of the derailment. The container had only a light load and this was found to be the worst condition for ride performance. As Sir Peter Parker once said – railways fall flat on their interfaces.

RAIB profile

Since its operational start up in 2005, the RAIB has gained a reputation for professional investigations, the unearthing of facts and the determination of causes. It is known to be fair and does not set out to apportion blame. The whole objective is to learn lessons from accidents that occur and to make recommendations that can minimise the chances of similar accidents happening again. It cannot mandate the industry but it is a brave organisation that chooses to ignore the findings.

The RAIB is very much in the public domain. Once an accident has occurred, a short notice will be posted on the RAIB website informing of what has happened and the areas of investigation. Once completed, which may take several months, the full reports are made public and they make fascinating reading. An average of four or five recommendations result from each accident report. Of these, 90% have been accepted, 7% await a response and 3% are not being implemented. Go to the RAIB site to register for receiving these.

The RAIB annual report gives details of all the types and categories of accident that occur. It is gratifying to know that signalling incidents, which because of SPADs were the prime reason for RAIB being created, now feature rarely as a major accident concern. We have moved on a long way in ten years.

Clive Kessell joined British Rail as an Engineering Student in 1961 and graduated via a thin sandwich course in Electrical Engineering from City University, London. He has been involved in railway telecommunications and signalling for his whole working life. He made telecommunications his primary expertise and became responsible for the roll out of Cab Secure Radio and the National Radio Network during the 1970s. He became Telecommunications Engineer for the Southern Region in 1979 and for all of BR in 1984.

Appointed Director, Engineering of BR Telecommunications in 1990, Clive moved to Racal in 1995 with privatisation and became Director, Engineering Services for Racal Fieldforce in 1999. He left mainstream employment in 2001 but still offers consultancy services to the rail industry through Centuria Comrail Ltd.

Clive has also been heavily involved with various railway industry bodies. He was President of the Institution of Railway Signal Engineers (IRSE) in 1999/2000 and Chairman of the Railway Engineers Forum (REF) from 2003 to 2007. He continues as a member of the IRSE International Technical Committee and is also a Liveryman of the Worshipful Company of Information Technologists.

A chartered engineer, Clive has presented many technical papers over the past 30 years and his wide experience has allowed him to write on a wide range of topics for Rail Engineer since 2007.